Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. Also, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a middle or large-sized battery pack having a plurality of battery cells electrically connected to each other because high power and large capacity are necessary for the middle or large-sized devices.
Preferably, a battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle or large-sized battery pack. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight, the manufacturing cost of the pouch-shaped battery is low, and it is easy to modify the shape of the pouch-shaped battery.
Meanwhile, in order for the battery module to provide power and capacity required by a predetermined apparatus or device, it is necessary to electrically connect a plurality of battery cells in series or in parallel to each other. As the capacity of the battery module is increased, it is necessary for the battery module to have easy expandability and a stable structure. Particularly in a case in which the battery module is configured using a plurality of battery cells or a plurality of cell modules, each of which includes a predetermined number of battery cells, a plurality of members, such as bus bars, for mechanical fastening and electrical connection therebetween is generally needed with the result that a process of assembling the mechanical fastening and electrical connection members is very complicated.
Furthermore, there is needed a space for coupling, welding, or soldering of the mechanical fastening and electrical connection members with the result that the total size of the battery system is increased. The increase in size of the battery system is not preferred in the above regard.
Also, the battery module is constituted by combining a plurality of battery cells, and therefore, safety and operational efficiency of the battery module assembly is greatly lowered when some of the battery cells suffer from overvoltage, overcurrent, or overheating. For this reason, means to sense and control such overvoltage, overcurrent, or overheating are needed. Consequently, voltage sensors are connected to the battery cells to check and control operational states of the battery cells in real time or at predetermined intervals. As the capacity of the battery module is increased, installation or connection of such sensing means very complicate a process of assembling the battery module. Furthermore, a plurality of wires is needed to install or connect the sensing means with the result that a short circuit may occur in the battery module. Also, the secondary battery is used as a power source for vehicles as a result of extension of the application range of the secondary battery. When strong impact or vibration is applied to the battery module, therefore, fastening means to stably maintain contact of the sensing means are needed.
Consequently, there is a high necessity for a bus bar assembly having a novel structure that is capable of fundamentally solving the above-mentioned problems.